Questions: Heat of formation of MgO Name: Liz Zharovsky Bench #: C19 Lab day and section: Tuesday - 2 1. Q1: Assess the accuracy for your value of ∆H f °(MgO,s). Discuss how the errors in the measurements of ∆H° rx for the two reactions contribute to the accuracy for your measured value of ∆H f °(MgO,s). What is the largest source of errors in this experiment? Sample calculation : REA of ∆H f °(MgO,s) = [(Average ∆H f °(MgO,s) – True ∆H f °(MgO,s)) / True ∆H f °(MgO,s)] x 100% = [(-639 kJ/mol – (-602 kJ/mol)) / -602 kJ/mol] x 100% = 6.14 % Answer : The relative error in accuracy is 6.14%, meaning there is a fairly significant error in accuracy, and the calculated heat of formation of MgO(s) deviates from the true value. In the measurements of ∆H° rx in the reactions between Mg and HCl and MgO and HCl, the calculated enthalpies directly affect the total heat of formation. This is because the ∆H° rx for each reaction is added together to determine the overall heat of
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